Refluxed Esterification of Fullerene-Conjugated P25 TiO₂ Promotes Free Radical Scavenging Capacity and Facilitates Antiaging Potentials in Human Cells

Titanium dioxide nanomaterials have good capability to prevent human cells from damage under UV irradiation. However, some studies indicated that the nanoscale of titanium dioxide could potentially cause harmful effects such as free radical generation under UV irradiation and thereby accelerate the progress of cell aging. Fullerenes can scavenge large amounts of free radicals due to the fact that fullerenes contain enormous amount of π electrons with low lying lowest unoccupied molecular orbital, but its adverse properties, such as the poor solubility in water, restricted the applicability. In this study, we employed water-soluble carboxylic acid fullerenes (C₆₀-COOH and C₇₀-COOH) as the free radical scavenger and modify onto the surface of titanium dioxide by refluxed esterification (P25/C₆₀-COOH or C₇₀-COOH) technique. The conformation and properties of these nanomaterials were characterized by techniques and equipment such as X-ray diffraction, energy dispersive spectroscopy analysis, scanning electron microscopy, thermal gravimetric analysis, high-resolution transmission electron microscopy, and Fourier transform infrared spectroscopy. We also introduced methylene blue and rhodamine B as indicators to evaluate and demonstrate the scavenging capacity of these nanomaterials. Moreover, we examined the biocompatibility and UV protection capacity of our P25/fullerene composites in human 293T cells, and applied luciferase activity assay to investigate the possible underlying cell protection mechanisms exhibited by these nanomaterials. Our data indicate that both P25/C₆₀-COOH and P25/C₇₀-COOH could protect human cells against UV exposure. P25/C₇₀-COOH exhibits great anti-inflammation capacity, whereas P25/C₆₀-COOH exhibits great anti-oxidative stress and anti-DNA damage capacity. Our results suggest that most of our P25/fullerene composite materials have the ability to reduce free radicals and exhibit high biomedical potential in anti-inflammation, anti-oxidant, and anti-aging applications.